There are several methods of encoding linear position. In one method, a cable attached to a movable platform is wound around a shaft, which is attached to an encoder of rotary motion. In another, a movable platform is attached to a nut threaded with a lead screw which is attached to a rotary encoder. A variation of this method is to move the platform by a stepper motor and keep count of the steps. Coarser encoding can be accomplished by electrical switches located at known positions which are opened and closed in turn by contact with a projection extending from a movable platform. Similarly, a beam of light, infrared, or other radiation can trigger radiation sensors in turn as the platform moves along a linear path. Although the combinations of lead screw and rotary encoder, or lead screw and stepper motor yield high accuracy, resolution, and repeatability, these methods are costly. Conversely, a series of switches or radiation detectors is economical but does not give very high positional resolution.
Sheets of optically transparent lenticular material are sometimes used for producing three-dimensional depth visualization effects and minor animation effects. In order to achieve these effects, it is necessary that the position on the lenticular material be precisely known in order to provide the depth visualization and animation effects. It is extremely complicated and subject to a high risk of error to manually align the lenticular print material for printing.